Flow control system

ABSTRACT

The present invention deals with an improved method and apparatus for measuring flow in fluid flow systems characterized by low flow rate. The invention utilizes the transit time or oscillatory frequency of a ball or float which moves along the direction of fluid flow and is returned to its original position by actuating a magnetic return system as it breaks a light beam or other sensing system. The cycle is repeated, with the transit time or oscillatory frequency being related to rate of fluid flow, and thus serving to indicate same for control purposes. The flow tube-ball measuring unit may take the form of a disposable insert into the flow measuring system.

United States Patent Spencer [45] May 16, 1972 FLOW CONTROL SYSTEMFOREIGN PATENTS OR APPLICATIONS [72] Inventor: Jordan L. Spencer, 560Riverside Drive, 895,364 5/1962 Great Britain ..73/ 194 R New York, NY10025 Primary Examiner-James J. Gill [22] filed 1971 Attorney-Robert l.Pearlman [21] Appl.No.: 131,945

Related U.S. Application Data ABSTRACT The present invention deals withan improved method and ap [62] Division of Ser. No. 831,351, June 9,1969, Pat. No. paratus for measuring flow in fluid flow systemscharacterized 3,605 74] by low flow rate. The invention utilizes thetransit time or oscillatory frequency of a ball or float which movesalong the 52 1 U.S. Cl ..73 194 E direction of fluid flow and isreturned to its Original Position y 51 Int. Cl. .001: 1/00 actuating amagnetic return System as it breaks a light beam or [58] Field of Search..73/194 E, 194R other Sensing System The cycle is repeated, with thetransit time or oscillatory frequency being related to rate of fluidflow and thus servin to indicate same for control u uses. 56 Refere cesC ted g P I 1 n I The flow tube-ball measuring unit may take the form ofa UNITED STATES T S disposable insert into the flow measuring system.

455,571 7/1891 Menzie ..73/194 R 12 Claims, 4 Drawing Figures EEWO l3L/GHT 554M 1 l n r0 Y FLU/D PATIENT 0 J 4 /9 1555 DETECTOR Z I PULSEPall/ER GE/VQPAMR AMPLIFIER COUNTER FREQUENCY METER FLOW CONTROL SYSTEMRELATED APPLICATIONS This is a divisional application of US. Ser. No.831,351, filed June 9, 1969 for the present inventor, now U.S. Pat. No.3,605,741.

BACKGROUND OF INVENTION Control of flow when utilizing extremely lowflow rates has presented a considerable problem. By way of example,intravenous feed means, e.g. for food, blood, drug, administration,etc., are used in numerous medical applications. Typically, a suitablechamber is provided as a reservoir of the solution to be fed, withtubing leading to an intravenous needle for injection at thevenipuncture point. A tube clamp is normally placed along the feed tubefor flow control. The proper and reliable control of the rate ofadministration of these fluids is essential to patient management andrecovery. It may vary from a few cubic centimeters per hour to severalcubic centimeters per minute. Drop counting by nurses has proven to behighly inefficient.

The methods heretofore employed for monitoring and controlling such lowflow rates have been time-consuming, and of limited accuracy.

The present invention serves to readily monitor and indicate low flowrates by automatic means, with a high degree of accuracy over a widerange of flow conditions. It can be combined with suitable warningdevices to indicate the cut-off of flow, or change above or below setlevels. Further, it can take the form of a low cost, disposabletube-and-ball assembly (sterile, if desired) which can readily beinserted into the fluid flow line so as to operate with a sensingmagnetic measuring unit.

SUMMARY OF INVENTION In accordance with the present invention, a ball orfloat responding to magnetic force is placed in a tubular section of theintravenous feed line. As the ball moves with fluid flow it cuts acrossa sensing device such as an optical sensor which inturn activatesmagnetic means which return the ball to its former position in the flowline. The ball then repeats its cycle. The frequency of the resultingoscillations is proportional to the fluid flow rate, and can be used toproduce an output which indicates flow rate. Altemately the transit timeof the ball across a portion of the tube can be determined. These inturn can be interrelated with suitable warning or control systems andthe like for adjusting flow to desired levels, target flows beingreadily indicated by the metering unit.

There are various modifications of the above-described systemessentially comprising a float or ball moving in a tube which isdetected and returned magnetically to its starting position, with flowrate being computed from the cycle periods for repeating the oscillatingmovement of the ball or float.

Any type of tubing suitable for flow of fluid can be used, e.g. glass,plastic, etc., of any desired cross-section (normally round).Particularly when employing the invention in the form of a disposabletube-float assembly, suitable stops are provided at the ends of the tubeinsert to prevent the float from leaving the tube, as will be made moreclearly apparent with reference to the drawings.

The float, which preferably is in the form of a ball, generally has across-sectional area about 50 to 80 percent of the tube cross-section,and can be made of various materials so long as it is responsive to amagnetic field for returning it to its initial position. It can be asphere of soft iron, with or without a coating to protect againstcorrosion. Alternatively, it can be a glass or plastic sphere with asoft iron core or having iron filings dispersed therein. In anembodiment particularly preferred for low flow rates and illustrated inFIG. 4, it may comprise a combination of a plastic whose densityapproximates that of the flowing fluid, and a second iron-containingsphere used to return the plastic sphere to its starting point.

The detection means for detennining that the float or ball has passed aselected point in the tube can also take various forms. It can be anoptical detector wherein the ball breaks or partially obscures a beam oflight which passes across the transparent tube and impinges on a photoresistor, photo tube or similar device. Alternatively, and especially inthe case of opaque fluids, the float can be relatively transparent, thuspermitting the flow of light to the photocell and resultant detection.

Inductive detectors can also be used. By the float or ball passingthrough or near a small coil of wire placed near or around the tube, itcan change the inductance of the coil and alter the frequency of anoscillator of which the coil is a part. Somewhat similarly, two platesof a capacitor which is connected to an oscillator circuit can beemployed. The movement of the ball between the plates changes thecapacitance, thus changing the frequency at which the oscillatoroperates.

Regardless of the type of detector utilized, it serves to actuateelectromagnetic means for returning the ball or float to its initialposition. The pole pieces of the magnet are placed on either side of thetube and shaped to give an inhomogenous magnetic field which exerts aforce on the float. When the detector has been stimulated by thecrossing of the float, it actuates a pulse of current of selectedamplitude and duration to cause the magnet to act on the float andsmoothly return it to its starting point. As illustrated in FIG. 4, twoor more magnets can be employed when utilizing a multiple ball system.

The means for computing and indicating flow by virtue of theoscillations of the ball-float can also be varied. The preferred methodis to determine the time necessary for the ball to traverse length L(the distance between its initial position and pointof detection andreturn), the resulting value being proportional to average fluidvelocity and thus volumetric flow. The combination of two detectors,starting a counter at an initial flow point and stopping it at thedetector, can be used. (The input to the counter is a fixed frequency.)The output of the counter system can be displayed directly or invertedto provide a digital signal proportional to flow which may be displayedon a standard meter or the like. More sophisticated systems forintegrating the flow signal to provide a signal proportional to totalvolume of fluid used can be combined with means for setting off an alarmor the like when a preset proportion of the intravenous feed reservoirhas been emptied.

The various aspects of the present invention will be made more clear byreference to the following drawings and accompanying description.

DRAWINGS FIG. 1 illustrates a basic system employing the presentinvention.

FIG. 2 depicts a ball float comprising an iron core surrounded by aplastic coating.

FIG. 3 shows a tube and flow assembly suitable as a sterile disposableelement.

FIG. 4 illustrates the use of multiple detectors and magnets forutilization with a multiple ball system especially suitable for low flowrates.

With reference to FIG. 1, shown therein is a simplified systemillustrating the present invention. For purpose of illustration, asystem for effecting intravenous feeding characterized by low flow rateswill be described, although the inven tion is applicable to all systemscharacterized by low flow rates.

Reservoir 10 contains the fluid to be injected intravenously suspendedby element 11. Tubing 12 serves as a passage for the fluid to beadministered with valve means 13 or other flow control element beingpositioned therein to vary flow rate, all as is conventional.

The remainder of tubing 12 is not shown other than tubing section 14which illustrates the operation of the present invention, and can besimply a portion of tubing 12 or an insert thereto as sown in FIG. 3.Tubing 14 in normal operation is preferably in horizontal position.

Float element 15, normally in the form of a ball or sphere is positionedin tubing section 14. It is responsive to magnetic force and may bemetallic, plastic with metal, e.g. iron, filing dispersed therein, orplastic or glass with a metallic core, the latter being illustrated byFIG. 2.

Magnetic means comprising soft iron poles 16 and 17 are positioned inproximity to said tube 14 at an upstream end thereof relative to thedirection of fluid flow.

Sensor means are positioned at a downstream portion of the tube denotedY, generally only about 0.5 to 1.5 inches from point X, the position ofthe magnetic means. As shown, the sensor means take the form of anoptical sensor of conventional type comprising light beam source 18 anddetector element 19.

Ball 15 is moved by the flow of fluid in the tube from its initialposition at X to point Y, at which time it crosses the light beamprovided by unit 18. The interruption of the light beam is translated toan electrical pulse of fixed duration by unit 20 and amplified byamplifier 21 so as to actuate magnets 16 and 17. The magnetic field thusformed serves to attract ball 15 and return it to its initial positionX. The magnetic force is halted when the pulse of current to the electromagnet ceases, and the cycle is then repeated with the ball 15 movingdown the tube responsive to fluid flow to again trip the sensing unit,etc.

The frequency of the cycles or ball oscillations thus created isproportional to the fluid flow rate through tubing 14. It is translatedinto an indication of fluid flow readily ascertained by the individualor mechanical and/or electrical means for altering fluid flow rate todescribed levels by flow control means 13 or the like.

In the system shown in FIG. 1 the pulse generated by detector 19 andunit 20 is fed to counter 22 which records the frequency of oscillationand transfers this information into a calibrated frequency or flow meterwhich directly indicates the rate of flow of the fluid.

The flow meter can be associated with an alarm unit to alert when flowhas dropped below a given level, or combined with an integrator systemto show total volume of fluid flow.

FIG. 3 depicts a disposable, sterile insert 30 which may be used inconjunction with the present invention. The magnetic, sensing andmetering unit may be a compact combination unit placed by the bedside ofthe patient, with an intravenous feed system and injection meansremovably connected thereto to permit change of fluids, removal to otherpatients, etc.

In such a system disposable element 30 containing ball float 36 acts assection tubing 14 of FIG. 1, and is placed between the sensing andmagnetic units in the approximate length between X and Y of FIG. 1.Normally this is done by simply connecting ends 31 and 32 into thenormal feed tubing 33 and 34 and clipping element 30 into proximity withthe sensing and magnetic means. Ends 31 and 32 preferably are of reducedcross section so that ball 36 remains therein during normal storage,handling, etc.

The disposable element of FIG. 3 may be plastic such as vinyl chlorideor polymethyl methacrylate, glass, etc., readily sterilized, insertedand disposed of to permit flexible and sterile utilization of thepresent system for measuring flow.

' FIG. 4 illustrates a more sophisticated system, especially suitablefor accurate measurement of low flow rates and comprising a dual float,magnet, and sensor system.

As described relative to FIG. 1, tubing section 50 may be in the normalconduit for flow of the intravenous liquid from reservoir to patient.Positioned therein are two balls P and I. Ball I is metallic, preferablyiron, and responsive to magnetic force. Ball P is plastic or glass andof similar density to the in travenous feed fluid so as to move almostfrictionlessly with the latters flow.

Initially both balls are at point M and magnets 51 and 51' are inactive.Magnet 56, 56 is then pulsed so as to move ball I rapidly towardposition M The flow of fluid then moves plastic ball P along tubing 15until it crosses the light beam of light source 54 alerting detector 55.The detector then actu- .ates magnets 51 and 51 in the same manner asdescribed relative to FIG. 1, returning ball I and along with it ball Pto point M This cycle is repeated at a frequency related to flow rate.

A second sensor unit 52, 53 may be utilized for improving the accuracyof the oscillation measurement and thus fluid flow. As ball P passes thelight beam from unit 52 it trips detector 53 which in turn resets andstarts a counter 57 which counts pulses from an oscillator 61. When ballP then crosses unit 54, 55 the counter 57 is stopped. The number ofpulses thus counted by counter 57 are in turn related to a flowindicator which has been calibrated to give fluid flow relative to theaccumulated count.

This count can also be used to actuate a controller 59, an alarm 58, aflow rate display 60, or similar system.

While the invention has particular advantage in controlling flow forintravenous feeding, it can be. used in other ways where extremely lowflow rates are involved and it is necessary to have a ready andinherently digital indication of flow not normally available byconventional flow meters, e.g. rotameters, and the like. I

Having described the present invention, that which is sought to beprotected is set forth in the following claims.

I claim:

1. Apparatus for indicating low volumetric rates of flow comprisingconduit means, a float element having a magnetic responsive materialassociated therewith positioned in said conduit, magnetic meanspositioned on an upstream section of said conduit and sensor meanspositioned at a downstream section of said conduit, said sensor meansactuating said magnetic means when said float element moving with thedirection of fluid flow crosses said sensor, thereby returning saidfloat element to its original position, and indicator means for relatingfluid flow to the cycles of said float element.

2. The apparatus of claim 1 wherein said float element is a ball ofnon-metallic material having sufficient iron therein to be responsive tosaid magnetic means.

3. The apparatus of claim 1 where said float means comprises a metalball.

4. The apparatus of claim 1 wherein said sensing element is an opticalsensor.

5. The apparatus of claim 1 wherein the pole pieces of said magneticmeans are placed on either side of said tube and shaped to give aninhomogenous magnetic field.

6. The apparatus of claim 1 which further comprises computing means forrelating the cyclic frequency of said float element to fluid flow rate.

7. The apparatus of claim 1 which further comprises control meansactuated by said means for indicating flow volume for adjusting fluidflow when it varies from a predetermined level.

8. The apparatus of claim 1 wherein said means for indicating fluid flowincludes tubing means having positioned therein a freely movable ballelement having a magnetic responsive material associated therewith, saidmagnetic means being positioned in proximity to said tubing means at anupstream portion thereof, sensing means positioned at a downstreamsection of said tubing means, said sensing means actuating said magneticmeans when said ball element crosses its position so as to return saidball to an initial position, and indicator means for relating fluid flowto the cycles of said ball element.

9. The apparatus of claim 8 comprising a metallic ball responsive tomagnetic force positioned in said tubing means, the action of saidmagnetic means on said metallic ball serving to return said plastic ballto its initial position.

10. The apparatus of claim 9 containing both a metallic ball element anda plastic ball element, and in which said means for indicating flowcomprises at least two sets of magnetic means, the upstream magnet beingactuated to initially move said metallic ball downstream ahead of saidplastic ball so as to permit the plastic ball to move freely with fluidflow before crossing said sensing element and initiating the magneticreturn of both balls to their initial position.

11. A disposable insert adapted to be used in the apparatus of claim 1comprising a relatively short length of tubing, float means having amagnetic responsive material associated therewith placed in said tubeand freely movable therein but contained by the ends of said tubing,said disposable insert being adapted to be inserted into said conduitmeans so as to co-act with said sensor and magnetic means, the cyclicmovement of said float means serving to indicate fluid flow. 5

12 The disposable insert of claim 11 wherein said float means is a ballhaving iron in its internal portion.

1. Apparatus for indicating low volumetric rates of flow comprisingconduit means, a float element having a magnetic responsive materialassociated therewith positioned in said conduit, magnetic meanspositioned on an upstream section of said conduit and sensor meanspositioned at a downstream section of said conduit, said sensor meansactuating said magnetic means when said float element moving with thedirection of fluid flow crosses said sensor, thereby returning saidfloat element to its original position, and indicator means for relatingfluid flow to the cycles of said float element.
 2. The apparatus ofclaim 1 wherein said float element is a ball of non-metallic materialhaving sufficient iron therein to be responsive to said magnetic means.3. The apparatus of claim 1 where said float means comprises a metalball.
 4. The apparatus of claim 1 wherein said sensing element is anoptical sensor.
 5. The apparatus of claim 1 wherein the pole pieces ofsaid magnetic means are placed on either side of said tube and shaped togive an inhomogenous magnetic field.
 6. The apparatus of claim 1 whichfurther comprises computing means for relating the cyclic frequency ofsaid float element to fluid flow rate.
 7. The apparatus of claim 1 whichfurther comprises control means actuated by said means for indicatingflow volume for adjusting fluid flow when it varies from a predeterminedleVel.
 8. The apparatus of claim 1 wherein said means for indicatingfluid flow includes tubing means having positioned therein a freelymovable ball element having a magnetic responsive material associatedtherewith, said magnetic means being positioned in proximity to saidtubing means at an upstream portion thereof, sensing means positioned ata downstream section of said tubing means, said sensing means actuatingsaid magnetic means when said ball element crosses its position so as toreturn said ball to an initial position, and indicator means forrelating fluid flow to the cycles of said ball element.
 9. The apparatusof claim 8 comprising a metallic ball responsive to magnetic forcepositioned in said tubing means, the action of said magnetic means onsaid metallic ball serving to return said plastic ball to its initialposition.
 10. The apparatus of claim 9 containing both a metallic ballelement and a plastic ball element, and in which said means forindicating flow comprises at least two sets of magnetic means, theupstream magnet being actuated to initially move said metallic balldownstream ahead of said plastic ball so as to permit the plastic ballto move freely with fluid flow before crossing said sensing element andinitiating the magnetic return of both balls to their initial position.11. A disposable insert adapted to be used in the apparatus of claim 1comprising a relatively short length of tubing, float means having amagnetic responsive material associated therewith placed in said tubeand freely movable therein but contained by the ends of said tubing,said disposable insert being adapted to be inserted into said conduitmeans so as to co-act with said sensor and magnetic means, the cyclicmovement of said float means serving to indicate fluid flow.
 12. Thedisposable insert of claim 11 wherein said float means is a ball havingiron in its internal portion.